Electrical switching devices are well known in the field of medium and high voltage switching applications. They are for example, used for interrupting a current, when an electrical fault occurs. As an example for an electrical switching device, circuit breakers have the task of opening contacts and keeping them far apart from one another in order to avoid a current flow, even if high electrical potential is originating from the electrical fault itself. For the purposes of this disclosure the term medium voltage refers to voltages from 1 kV to 72.5 kV and the term high voltage refers to voltages higher than 72.5 kV. The electrical switching devices, like the circuit breakers, may have to be able to carry high nominal currents of 5000 A to 6300 A and to switch very high short circuit currents of 63 kA to 80 kA at very high voltages of 550 kV to 1200 kV.
Because of the high nominal current, the electrical switching devices of today require many so-called nominal contact fingers for the nominal current. When disconnecting (opening) a nominal or short circuit current within the electrical switching devices, the current commutates from nominal contacts of the electrical switching device to its contacts. Thus, when connecting (closing) the nominal contacts of the electric switching device, also the arcing contacts are connected. They can include as a first arcing contact arcing contact fingers arranged around the longitudinal axis of the electrical switching device in a so-called arcing finger cage and, as a second arcing contact, a rod which is driven into the linger cage.
The opening and closing processes of the nominal and the arcing contacts have to be carried out with a predefined speed, according to the specification of the electrical switching device. During the closing of the electrical switching, device particularly the arcing contact fingers are subjected to an impact caused by the incoming rod. The impact force acting on the arcing contact fingers depends on the relative closing speed of the contact fingers and the rod. Thus, the higher the speed, the higher is the force acting on the arcing contact fingers. However, a high contact speed is desired, because it improves the performance of the electrical switching device. As a consequence of higher impact forces acting, on the arcing contact fingers, the arcing contact fingers may experience a permanent deformation or ma break. For example, they may be deformed radially outward with respect to the longitudinal axis or may fall apart. A contact force between the arcing contact finger and the second arcing contact has to be high enough to ensure a good electrical contact. Eventually, requirements regarding to contact forces are not met an more because of the deformation.